1. Field of the Invention
The present invention relates generally to circuit breakers and, more particularly, to a shock-resistant solenoid assembly with an inertia lock for use in a circuit breaker.
2. Description of the Related Art
Numerous types of circuit breakers are known and understood in the relevant art. Among the purposes for which circuit breakers are provided is to interrupt current on demand or under certain defined circumstances. In this regard, multi-phase circuit breakers typically include a trip unit that can simultaneously open the contacts of all of the phases to interrupt electrical current. The trip unit typically includes a latch mechanism that rotates a crossbar to pivot movable contacts away from stationary contacts on demand.
While the latch mechanism is typically operated automatically during specified overcurrent and under-voltage conditions, it is often desirable to additionally provide a mechanical trip plunger on the trip unit that can operate the latch mechanism to permit the circuit breaker to be tripped manually as needed. A solenoid or shunt is typically provided to selectively engage the trip plunger to operate the latch mechanism.
While such tripping solenoids operate reliably under many conditions, circuit breaker trip mechanisms employing such tripping solenoids are often subject to inadvertent tripping during shock loading of the circuit breaker. As is known in the relevant art, a solenoid includes a core that is axially-movable with respect to the solenoid housing. During shock loading of the circuit breaker, the core of the tripping solenoid can be induced to move with respect to the solenoid housing, which can result in the core engaging the trip plunger to inappropriately trip the circuit breaker, even though the solenoid is in a deenergized condition. Such inappropriate tripping of a circuit breaker is to be particularly avoided in critical applications in which loss of power would create an unsafe or harmful condition. It is thus desired to provide a circuit breaker solenoid assembly or shunt trip apparatus that is resistant to shock loading yet is capable of engaging on command the trip plunger of a circuit breaker trip unit.
In accordance with the invention, a shock-resistant solenoid assembly includes a trip solenoid and an inertia lock, with the inertia lock being operable to resist unintended engagement of a core of the trip solenoid with a trip plunger of a trip unit of a circuit breaker. The core is movable along a tripping path between a retracted position and an extended position, with the core engaging the trip plunger in the extended position. The inertia lock includes an inertia member and a latch. In response to shock loading, the inertia member interposes the latch into the tripping path to engage the core and resist the core from operatively engaging the tripping plunger under inappropriate conditions.
In view of the foregoing, an objective of the present invention is to provide a solenoid assembly that is shock-resistant.
Another objective of the present invention is to provide a solenoid assembly that includes an inertia lock.
Another objective of the present invention is to provide a solenoid assembly that can selectively engage a trip plunger of a trip unit to trip a circuit breaker on command, yet that is resistant to shock loading.
An aspect of the present invention is to provide a shock-resistant solenoid assembly for selectively engaging a trip plunger of a trip unit of a circuit breaker and for resisting inappropriate engagement of the trip plunger in response to a shock load, the general nature of which can be stated as including a trip solenoid having a core movable along a tripping path between a retracted position and an extended position, in which the core in the extended position is engaged with the trip plunger, and an inertia lock having an inertia member operatively connected with a latch, the latch being disposed on a mount and being actuatable by the inertia member in response to the shock load to engage the core to restrain movement of the core to the extended position.
Another aspect of the present invention is to provide a shock-resistant solenoid assembly in which the latch is movable between a rest position and an activated position, in which the latch, in the activated position, engages the core. The latch is biased to the rest position by a first biasing device, and the latch in the rest position is outside the tripping path.
Another aspect of the present invention is to provide a shock-resistant solenoid assembly in which the latch is pivotably mounted on the mount.
Another aspect of the present invention is to provide a circuit breaker, the general nature of which can be stated as including a trip unit having a trip plunger, a shock-resistant solenoid assembly for selectively engaging the trip plunger and for resisting inappropriate engagement of the trip plunger in response to a shock load, the shock-resistant solenoid assembly including a trip solenoid and an inertia lock, the trip solenoid having a core movable along a tripping path between a retracted position and an extended position, in which the core in the extended position is engaged with the trip plunger, and the inertia lock having an inertia member operatively connected with a latch, the latch being disposed on a mount and being actuatable by the inertia member in response to the shock load to engage the core to restrain movement of the core to the extended position.
Still another aspect of the present invention is to provide a method of resisting a core from engaging a trip plunger of a trip unit of a circuit breaker in response to a shock load, the plunger being movable along a tripping path between a retracted position and an extended position, the plunger in the extended position engaging the trip plunger, the general nature of which can be stated as including the steps of moving an inertia lock into the tripping path in response to the shock load and contacting the core with the inertia lock at a point between the extended and retracted positions to resist the core from engaging the trip plunger.
Another aspect of the present invention is to provide a method of resisting a core from engaging a trip plunger in which the step of moving the inertia lock into the tripping path included the steps of repositioning the inertia lock from a rest position to an activated position and overcoming the bias of a biasing device that biases the inertia lock to the rest position.
Another aspect of the present invention is to provide a method of resisting a core from engaging a trip plunger in which the step of contact in the core includes the step of resisting relative movement between the core and the trip plunger in a direction toward the extended position.